High SEER systems

[ruud-man]

With the new SEER standard rapidly approaching,I have some concerns with the higher specific heat ratios of these systems. I know some mfgrs offer demand dehumidification as an option with their ECM equipped airhandlers/ furnaces.

The idea is to decrease the SHR by slowing the blower, thus decreasing the cfm per ton. I really don't see this as the "end all" solution.

What I do see is the need to operate some sort of stand alone dehumidifier, be it whole house or room unit. Maybe even utilizing an ERV to lower moisture buld up in the conditioned space.

In other words are the savings there. Operating a dehumififier and or and ERV certainly has to be brought into the equation.

Another conern is I'm already seeing airhandlers/ furnaces using a blower motor that is a cross between an ECM and a PSC motor. The new motor does not maintain cfm as the ECM does, but it does operate at about the same effeciency. And since it is not as controllable as the ECM,I wonder if demand dehumididfication can be an option.

Of course the new motor has been developed to make the 13 SEER basic equipment more competitive (builder's model, etc). I doubt if these systems will be installed along with the added expense of dehumidifiers and ERVs.

Now we have a system with high SHF and a very uncomfortable, unhappy customer who can't understand why this new high effecincy system is not as comfortable as that old 10SEER they just replaced.

Any other concerns out thers?

[teddy bear]

The complexity and equipment cost of being able to change the a/c operating specifications on the fly is not a good value. As you see from the posted problems of setting up these complex systems, maintaining them for 10-15 years will be more challenging. In addition they are unable to provide humidity control with low/no cooling loads or while providing fresh air ventilation. Hence your concerns about dehumidification/ERVs are important.
A high SEER a/c sized to handle extra occupants and a two hour cool-down from a t-stat "elevated temp"(opposite set-back) makes the most sense. In well built homes, with tight, well insulated ducts, and proper set-up, the a/c will maintain 50%RH with a +75% a/c duty cycle during high outdoor humidity. Combining the a/c with a whole house ventilating dehumidifier provides the desired amount of fresh air ventilation when the home is occupied. The dehu maintains 50%RH when the a/c is in the "temp set-up" mode or during low/no cooling load. Daily "temperature set-up" when the house is unoccupied may reduce a/c energy by 25%-35% . The daily "temp set-up" mode also allows the a/c ducts a "dry-out" time. Also exterior walls will dry-out verses condensing exterior moisture on the outside of the drywall. The drying helps reduces mold growth potiential. Regarding ERVs, prefer pressurizing the home with 50-75 cfm of make-up air when the home is occupied. This also supplies make-up air for the clothes drier, bath fans, and other appliances. If large quantities of continuous ventilation are required, ERVs are justified.

Regarding "proper a/c setup" , high SEER a/c require a very cold coil temperature like 40^F-45^F. Insulating ducts with an adequate exterior vapor barrier to avoid sweating is neccesary.
The cost of high SEER a/c combined with a top quality ventilating dehumidifier is less than the max featured multi-speed a/c. Indoor air quality and comfort will better a/c-dehu combination. A "recovering" dehu peddler, TB

[ruud-man]

I understand and pretty much agree about the initial cost being less for the high SEER w/ a dehumidifier.

I am questioning the economics of operation. One 12 SEER in operation vs. a 13 SEER being augmented with a dehumidifier or ER just to retain the comfort level that the 12 SEER provided.

In other words, are we being taken for a ride by the DOE? The jump to 13 SEER reminds me of the prohibition of standing pilots. The ultimate energy savings for the individual home owner is miniscule. However, the sum of the entire national households would be a large savings for the cuountry as a whole.

The pilot thing seemed to work, but this 13 SEER deal appears to be smoke and mirrors. Where are the savings for anyone? If one considers the power for the AC plus the power for the dehumidifier or ERV, maybe we are right back where we started.

IMHO...